Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (137 page)

Figure 5–4
Algorithm for spontaneous bacterial peritonitis. PMN, polymorphonuclear leukocytes.

PRIMARY PERITONITIS

Ascites fluid findings
: Gram stain of direct smear and culture of peritoneal fluid usually shows streptococci in children. In adults, it is caused by
E. coli
(40–60%) or
S. pneumoniae
(15%), other gram-negative bacilli, and enterococci; usually one organism. May be caused by
Mycobacterium tuberculosis
. Marked increase in WBC (≤50,000/μL) and PMN (80–90%).

Peritoneal lavage fluid findings
: Shows WBC count >200/μL in 99% of cases.
Other
: Laboratory findings due to nephrotic syndrome and post–necrotic cirrhosis and occasionally bacteremia in children and cirrhosis with ascites in adults.

SECONDARY PERITONITIS

Occurs and recurs very frequently in continuous ambulatory peritoneal dialysis.

Laboratory findings due perforation of hollow viscus (e.g., appendicitis, perforated ulcer).

Dialysate findings
: Turbid (indicates >300 WBC/μL); Gram stain, culture, and leukocytosis may be absent. Caused by gram-positive bacteria in approximately 70%, enteric gram-negative bacilli and
P. aeruginosa
in 20–30%, others in 10–20%, and sterile in 10–20%.
If more than one pathogen is found, rule out perforated viscus.
Usually more than one organism is found.

Suggested Readings

Cárdenas A, Gelrud A, Chopra S. Chylous, bloody, and pancreatic ascites.
www.uptodate.com
, May 2009.

Khan F, Sachs H, Pechet L, et al.
Guide to Diagnostic Testing
. Philadelphia, PA: Lippincott Williams & Wilkins; 2002.

Runyon B. Diagnosis and evaluation of patients with ascites.
www.uptodate.com
, May 2009.

Runyon B. Diagnosis of spontaneous bacterial peritonitis.
www.uptodate.com
, May 2009.

DIARRHEA

   Definition

   Diarrhea is defined as >200 g of stool or an increase in the frequency or fluidity of normal stools. It may be acute or chronic, and it is considered chronic when it lasts at least 4 weeks.

   Etiology

Diarrhea can result from any of the following mechanisms.

1.   Osmosis: Molecules not normally present in the intestinal lumen increase the osmolality of chime, drawing water into the lumen (i.e., lactose)

2.   Secretion: Substances can cause intestinal cells to secrete sodium and water (i.e., cholera toxin).

3.   Inflammation results in denuding of the intestinal lining, which in turn disrupts normal absorption, thereby allowing compounds from the lining to leak into the lumen resulting in an increased osmosis.

4.   Motility: Hypermotility leads to an increased stool volume. Hypomotility can lead to bacterial overgrowth, which causes diarrhea through several different mechanisms.

5.   Anal sphincter dysfunction causes fecal incontinence, which can be interpreted by the patient as diarrhea.

   Differential Diagnosis

1.   Laxative abuse accounts for approximately 15% of all chronic causes. It should be suspected in patients with a mental health disorder.

2.   Sorbitol can cause diarrhea. In one study, approximately 17% of people had diarrhea following the ingestion of 4–5 minutes containing sorbitol.

3.   Both bile salts and fatty acids cause secretion of chloride followed by water into the colon. Excess bile salts also lead to a mild degree of fat malabsorption.

4.   Bacterial overgrowth can occur secondary to diabetes, blind loop syndrome, amyloidosis, diverticulitis, and scleroderma, among other causes.

5.   Irritable bowel syndrome classically presents with diarrhea alternating with constipation, but it can also occur in a diarrhea-predominant form.

6.   Gastric surgery syndrome results in a decreased contact time with the luminal surface and decreased digestive juices mixing with the chyme.

7.   Hyperthyroidism usually has increased frequency and amount of diarrhea but not fluidity. Diarrhea is present in approximately 25% of hyperthyroid cases.

8.   Inflammatory bowel disease (IBD):

   Ulcerative colitis is a relapsing and remitting disease that leads to acute inflammation of the colorectal mucosa. The rectum is involved in 55% of cases. In severe cases, bloody diarrhea often leads to weight loss, anemia, and electrolyte imbalance.

   Crohn disease is a chronic relapsing disorder characterized by transmural, asymmetric, and segmental inflammation. It typically involves the ileum, colon, or perianal region; right lower quadrant pain associated with bloody diarrhea is present in 80% of patients.

9. Neoplasia:

   Villous adenoma produces prostaglandins, which stimulate chloride and water secretion from the colon.

   Serotonin from carcinoid cells stimulates gut motility and increases intestinal secretion.